Roll-to-roll atomic layer deposition of titania nanocoating on thermally stabilizing lithium nickel cobalt manganese oxide cathodes for lithium ion batteries

Conformal coating of ceramic layers (nm-thick) on Ni-rich layered cathode materials is an effective strategy for improving high-temperature longevity of Li-ion batteries (LIBs). In this work, we develop a roll-to-roll atomic layer deposition (R2R ALD) apparatus for growing uniform nanolayers of TiO₂. We explore the effect of ALD parameters (temperature: 120−180 °C and line speed: 2−40 mm s⁻¹) on the TiO₂ surface coating and subsequently investigate the electrochemical performance of the as-prepared cathodes. The capacity retention of TiO₂-coated porous electrodes is substantially improved compared to that of the pristine cathode material for high-temperature cycling. Electrochemical impedance spectroscopy confirms that the ALD-TiO₂ coating suppresses the undesired side reactions initiated at the electrode/electrolyte interface, reduces charge transfer resistance, and ultimately facilitates the Li⁺ transport through the composite cathode nanostructure. The robust design of the ALD-TiO₂ cathode material enables high-temperature operation (>55 °C) with enhanced specific capacity, superior rate capability, excellent cyclability, and ultra-high coulombic efficiency within a wide potential window (3.0−4.35 V). The R2R ALD technique developed in this work paves the way for large-scale fabrication of ceramic-coated cathode sheets with a production rate reaching 2.4 m min⁻¹ for a continuous coating operation.